Florian Engert

Research Interests:

The general goal of the laboratory is the comprehensive identification
and examination of neural circuits controlling behavior using the larval
zebrafish as a model system. To that end, we have established and quantified
a series of visually induced behaviors and analyzed the individual resulting
motor components. Using these assays in combination with various calcium
indicators and two-photon microscopy we have monitored neuronal activity
throughout the fish brain in an awake and intact preparation. An extended
goal is the study of how changes or variations in the behavior are reflected
in changes in the underlying neuronal activity. To that end, we have developed
several quantitative learning assays and tools for in vivo monitoring
of neural activity in freely swimming larvae.

Background:

Neuroscientists have long been working to understand how biological structures
can produce the complex behaviors that are generated by the nervous system.
However, even the basic operational principles governing a brain’s
interconnected network of cells have remained painfully elusive. My laboratory
is working on a scientific strategy focused on building a complete, multi-level
picture of simple neural circuits that will advance our basic understanding
of brain function and offers a complete view into the neuronal activity
underlying a series of relatively complex behaviors.

Generally the question of how the brain, or neural circuits
in particular, function ought to be reduced to the question of what the
brain or particular parts of the brain are doing. This is best addresses
by rigorous and quantitative behavioral assays that allow us to relate
a particular set of input stimuli – in our case visual signals that
get translated by the retina into action potentials in ganglion cells
– to a set of motor actions that are controlled by an array of spikes
in motor neurons – the output of the system. Both data-sets can
be assessed to a first order by behavioral experiments. The second question
then has to be how the neurons and synapses within the circuit actually
perform this computation. Important insights into this problem can be
gained by recording activity in every neuron of the fish’s brain
in the context of a specific behavior. This would be a truly daunting
task in any mammalian preparation but the small and transparent brain
of the larval zebrafish allowed us to develop and extend the technology
that makes it possible to acquire these datasets in fish expressing genetically
encoded indicators in all neurons1. In parallel we have tried to simplify
the question by the examination of individual modules in the brain. Here,
we have started to make progress by finding specific nuclei in the fish
brain - the optic tectum which processes inputs directly from the retina2
on the one hand and the reticular spinal formation, a set of identified
neurons that exclusively controls behavior3,4, on the other hand - that
provide stepping stones on the long journey to a complete understanding
of the brain and its role in producing behavior.